[quote]
IOS Code : Letter Feature
a : APPN
a2 : ATM
a3 : SNASW
b : Appletalk Routing
c : Remote Access Server
d : Desktop routing
dsc : Dial Shelf Controller
g5 : Enterprise Wireless (7200)
g6 : GPRS Gateway Support Node (7200)
i : IP routing
i5 : IP routing, no ISDN (mc3810)
in : Base IP (8500CSR)
j : Enterprise (kitchen sink routing)
n : IPX Routing (low-end routers)
p : Service Provider (or DOCSIS for uBR)
r(x) : IBM
telco : Telco
w3 : Distributed Director
wp : IP/ATM Base Image (8500MSR,LS1010)
y/y5 : IP Routing (low-end routers) (missing some IP routing/features like BGP)
y7 : IP/ADSL
56i : Encryption(DES)
ent : Plus (only when used with 'telco')
k1 : BPI
k2/k8/k9 : Encryption(DES=k8, 3DES=k9)
o : Firewall
o3 : Firewall/IDS
s : Plus, or "LAN Only" on Cat6K/7600
s2 : Voice IP to IP Voice Gateway (26xx/36xx/37xx only)
s3 : "Basic" (limited IP routing, for limited-memory 26xx, 36xx)
s4 : "Basic" without switching
s5 : "Basic" without HD analog/AIM/Voice
t : Telco Return
v : VIP Support
v3,v8 : Voice (17xx) - v3=VOICE, v8=VOX
w6 : Wireless
x(or x2) : MCM
 
l : Runs from Flash
m : Runs from RAM
z : Compressed image
 
For Newer Images
 
Image Name : Feature Set
cxxxx-ipbase-mz : IP Base
cxxxx-ipvoice-mz : IP Voice
cxxxx-advsecurityk9-mz : Advanced Security (note k9=strong encryption)
cxxxx-spservicesk9-mz : Service Provider Services (note: also known as SP Services)
cxxxx-entbase-mz : Enterprise Base
cxxxx-advipservicesk9-mz : Advanced IP Services
cxxxx-entservicesk9-mz : Enterprise Services
cxxxx-adventerprisek9-mz : Advanced Enterprise Services
[/quote]